Polymer electrolyte membranes may be used in fuel cells, which provide a clean, alternative power source for automotive and portable applications. The polymer electrolyte membrane should have high proton conductivity, good chemical and mechanical stability, good dimensional stability and strength. Perfluorosulfonic acid polymers, such as Nafion®, provide good conductivity and are often used in polymer electrolyte membranes. These materials can be quite costly to use and are susceptible to dimensional changes from swelling and shrinking, which can cause structural failure of the membrane resulting in cracks, tears or other deformations.
Preformed networks or porous supports and crosslinked networks of nonconductive materials are often used in membranes to provide strength and stability. Electrolytes are imbedded into the pores of the porous support to provide conductivity and are prevented from swelling by the network structure of the porous support. Silanes with acid functional groups have been used as starting materials for electrolytes, but the resulting membranes can be too brittle.
What is needed is a polymer electrolyte membrane having improved mechanical strength and dimensional stability with increased acid functional groups for improved conductivity.